Sonic Comparison between New Tung Sol 6550 vs KT120 vs KT150

[Joe Dawson]

Has anyone performed a sonic comparison between the three tubes? Do they sound Exactly alike, or
sonically different? If different, how sonically different?

How about longevity?

Thanks

pos

 

[kward]

I think the TS KT120 is an overall better sounding tube. The KT120 has just an overall well put together even-keeled sound. It’s been too long for me to characterize detailed differences between it and the new production 6550, but for my tastes, the KT120 hits the sweet spot.

No experience with the KT150.

 

[trainbuftony]

People always compare things.
Unfortunately very few of them list what test conditions they used to obtain their result, and virtually none of them provide any measurements.
Take it all with a grain of salt.
Determine what power level you need.
Use power tubes which get you to that power level using the topology of your choice. Run them about 70 to 80% of maximum disapation and replace them when they get weak.
There's no magic to it.
There's a lot of opinions floating about which are completely irrelevant because they do not come with test conditions and often the tests are performed on worn out antique equipment, then used by the uninitiated to make grand proclamations about how a tube sounds.
Tubes don't really have much of a sound.
Speakers have a sound, cartridges have a sound, but tubes, they just do their job, or they don't.
Don't read too deep into the tube rolling topic, you'll go insane.
Instead find some technical literature about how tubes work, how to set up a power stage and how to minimize distortion by basing hot and balancing your phase inverter. You'll be lightyears ahead of those who only know how to roll tubes. Unfortunately, the rollers will always be louder and there will be a lot of them spreading their noise.

 

[kward]

^^ good points. This is all subjective. My experimentation was done in a push pull amp with a moderate 12 dB feedback. Your mileage may vary as they say. For example how they differ in a SE amp may be totally different.

 

[gadget73]

Haven't done it specifically with a TS KT88, but I have done it with EH and Gold Lion KT88. I thought the KT-120 had a little better bottom end than either, but the Gold Lion had slightly better midrange. Of the three the EH came in last place. I'm currently running KT90 which have similar midrange to the GL KT88.

None of them are bad sounding tubes by any stretch but given the chance to listen to them all in the same amps and with all the rest of the stuff the same, something has to be the winner.

JMO but if you're getting vast changes in sonics from changing the tubes, something is probably wrong. The only time I've ever had it happen was when a bad tube was swapped for a good or vise-versa.

 

[dcgibby]

I haven't tried the KT120, but to my ears the KT150 is superior to the 6550. The KT150 seems quite transparent and neutral compared to the 6550. Where the 6550 struggles, the KT150 is effortless.

 

[trainbuftony]

I haven't tried the KT120, but to my ears the KT150 is superior to the 6550. The KT150 seems quite transparent and neutral compared to the 6550. Where the 6550 struggles, the KT150 is effortless.

Perfect example of what I mentioned.
What amplifier?
Push pull, single ended?
Triode, pentode or ultralinear?
Primary impedence?
How much feedback?
Cathode biased or fixed?
What percentage of max dissipation were they running at, bias wise?

All of these factors are going to have a significant impact on the sound you perceive the amplifier to make.
Any observations about a tubes sound are not relevant without a whole bunch more info, which the average tube user is not going to be capable of or willing to, represent accurately.

 

[Joe Dawson]

People always compare things.
Unfortunately very few of them list what test conditions they used to obtain their result, and virtually none of them provide any measurements.
Take it all with a grain of salt.
Determine what power level you need.
Use power tubes which get you to that power level using the topology of your choice. Run them about 70 to 80% of maximum disapation and replace them when they get weak.
There's no magic to it.
There's a lot of opinions floating about which are completely irrelevant because they do not come with test conditions and often the tests are performed on worn out antique equipment, then used by the uninitiated to make grand proclamations about how a tube sounds.
Tubes don't really have much of a sound.
Speakers have a sound, cartridges have a sound, but tubes, they just do their job, or they don't.
Don't read too deep into the tube rolling topic, you'll go insane.
Instead find some technical literature about how tubes work, how to set up a power stage and how to minimize distortion by basing hot and balancing your phase inverter. You'll be lightyears ahead of those who only know how to roll tubes. Unfortunately, the rollers will always be louder and there will be a lot of them spreading their noise.

I assumed all understood I was asking if there is a sonic difference between the TS 6550 vs the
TS KT120 in the same circuit, under the same conditions. I apologize for not being more clear.
I do not want my monoblocks sounding different with the KT120s as the TS 6550 is perfect for my design.

Pertaining to the quote above:

1. Different tubes certainly do have a "sound" quality in a high quality amplifier for several reasons.
A. The harmonic structure can be and is different between brands, and even different tubes of the same manufacturer.
A chinese KT88 has a different harmonic structure, and twice the HD of a Winged C KT88 under the same conditions.
B. One has to also be aware of different materials and material quality.
I won't go any deeper.

2. When comparing tubes, the system is the same, so the conditions are basically the same and cancels out of the equation.
Now if the tube's characteristics are quite different when comparing, that needs to be considered.

3. If one tube sounds better, then there is a sonic difference. I am Not requesting which sounds best, but
if there is a sonic difference between the new Tung Sol 6550 and their KT120. I may be
able to design around a different "sound", but not necessarily.

I want to know if I will obtain the same sonics from my monoblocks with the new TS KT120s as with the new TS 6550s.
Thanks.

keep on truckin

joe

 

[trainbuftony]

There's no way for us to answer that on a factual basis.
Inn general, if you put in a higher rated tube, you need to bias it hotter (more current) to get it to perform without crossover distortion. That will tax your power supply and reveal its Sag characteristics, which often get confused for "sonic differences" in tubes, they're not differences in the tubes themselves so much as they're deficiencies in the power supply.
An adequate power supply for KT150s can easily run 120s or 6550/kt88 by setting the bias to 70-80% of max for the tube type used.
Going the other way, stretching a smaller power supply to run bigger tubes is going to cause voltage sag, which gets worse the more you ask from the amp. Your ear will hear that, but it's not a difference in the tubes "sonics" it's directly related to its ability to pull current, and the power supply's inability to satiate this demand.
Go ahead, measure it.

 

[Joe Dawson]

There's no way for us to answer that on a factual basis.
Inn general, if you put in a higher rated tube, you need to bias it hotter (more current) to get it to perform without crossover distortion. That will tax your power supply and reveal its Sag characteristics, which often get confused for "sonic differences" in tubes, they're not differences in the tubes themselves so much as they're deficiencies in the power supply.
An adequate power supply for KT150s can easily run 120s or 6550/kt88 by setting the bias to 70-80% of max for the tube type used.
Going the other way, stretching a smaller power supply to run bigger tubes is going to cause voltage sag, which gets worse the more you ask from the amp. Your ear will hear that, but it's not a difference in the tubes "sonics" it's directly related to its ability to pull current, and the power supply's inability to satiate this demand.
Go ahead, measure it.

Checking the tubes, the interlectrode capacitances are closer between a KT88 and KT150 than the KT120, but not that much.
Compared to previous output, wiring, and Miller capacitance, a couple of pf won't make minimal difference.

Transconductance is within 13% or so between tubes. That would be within the range of manufactured tube tolerances in
general. Rp (plate resistance), Mu is within manufacturer's tolerances.

Any difference of Materials used vs the other tube is of a concern. Material quality would be consistent.

Unfortunately, crossover distortion has no relevance to the higher rated tube in terms of plate dissipation and above conditions
are similar. The rest of the post is therefore not relevant.

keep on truckin

joe

 

[dcgibby]

Perfect example of what I mentioned.
What amplifier?
Push pull, single ended?
Triode, pentode or ultralinear?
Primary impedence?
How much feedback?
Cathode biased or fixed?
What percentage of max dissipation were they running at, bias wise?

All of these factors are going to have a significant impact on the sound you perceive the amplifier to make.
Any observations about a tubes sound are not relevant without a whole bunch more info, which the average tube user is not going to be capable of or willing to, represent accurately.

You are no doubt correct. My comparison of these tubes uses two very different amplifiers so my take may be completely off the wall. But it's just an opinion, worth about as much as anything else on the internet.

 

[Joe Dawson]

Sigh.

Whether it is run PP, SET, negative feedback or not, cathode bias or fixed bias etc, we are comparing the
TS 6550 and TS KT120 tubes under identical parts/conditions. A legit question might be if temperature changes
affect the characteristics that much between the TS 6550 and KT120.

But that is exactly the question we are attempting to answer by performing the listening comparison.

I guess the question could be raised, is the amplifier/system so poor that one cannot tell the difference but I have not
seen that response raised.

keep on truckin

joe

 

[kward]

You also asked the longevity question. I would think if the 6550 and KT120 are used interchangeably in the same circuit that is designed for a 6550, they would have equivalent longevity characteristics.

The question is when you crank up the idle current, still under the max plate dissipation for the KT120 but higher than the max for the 6550, how does the longevity change? Or let’s say you idle both at 80% of their respective max plate dissipation, does one have higher longevity than the other? I’ve not done those sorts of tests, but it would be interesting to see those results if someone has done that sort of long term testing.

 

[gadget73]

guess the question could be raised, is the amplifier/system so poor that one cannot tell the difference

or its so good that it negates any changes. I like things that aren't fussy about their tubes. I'm OK with it sounding slightly different but I don't want things that are going to force me on an endless path of trying every tube combo imaginable in order to find the magic mixture.

then again the chronic ringing in my ears doesn't exactly help me be overly discerning to small variations in things.

 

[crispycircuit]

I like it when your Happy right away! And feel like like your done...

 

[oldflame]

Apparently knowledgeable sources have indicated that the KT-120 was developed specifically for audio, so I'll guess the KT-150 was too. Nothing definitive, but I've
read, more often, that the 120 seems to find more love than the other choices. Of course, the particular amp and system can affect that.

In my Rogue Atlas, there's no way a 6500/KT-88 would have the power or bass of the KT-120, but that amp was redesigned for the newer tube.

 

[oldflame]

I just dug up a May, 2013, Stereophile review of the ARC Reference 75, which uses the KT-120's. The author discusses the KT-120 vs 6550 and you may find it interesting.

 

[opnly bafld]

Audio Research Reference 75 power amplifier

After I read Brian Damkroger's rave review of the Audio Research Corporation's Reference 5 SE line stage in the November 2012 Stereophile, I was excited about getting the review sample into my system so that I could do a Follow-Up (February 2013). However, the sample had already been returned to...

www.stereophile.com

 

[crispycircuit]

Well the premium price of the 120 should have premium sound, eh?

 

[BmWr75]

Sigh.

You have asked a question for which there is no answer since you specifically want to know how they will sound in your two mono-block amps. Didn't see where you ever identified the make/model of your amps either.